Physical activity may modestly reduce weight and body fat in obese adolescents

They included 30 randomised controlled trials (1,508 participants, median publication year 2017) conducted across 15 countries, with participants aged 10–17 years. When any form of physical activity was compared to no intervention, the review found low-certainty evidence of small improvements: body weight decreased by a mean of 1.88 kg, waist circumference by 2.88 cm, and body fat percentage by 2.96%. However, very low-certainty evidence existed for effects on BMI, BMI z-score, glucose, and insulin resistance. Mental well-being outcomes (self-esteem, self-efficacy, self-perception) showed modest improvements in one small study of 56 participants. A major limitation was that all included studies were assessed as high risk of bias, and the certainty of evidence was substantially weakened by methodological flaws, clinical and statistical heterogeneity, and small sample sizes. Importantly, no included studies reported on quality of life, adverse events, comorbidities, or whether weight loss persisted into adulthood.

The meta-analysis pooled results from trials lasting at least 12 weeks, comparing any physical activity (varying in type, intensity, and frequency) against no intervention. Body weight reduction of roughly 2 kg is clinically small—equivalent to a 1–2% loss for a 100 kg adolescent. Reductions in BMI z-score were negligible (−0.01 units), and heterogeneity was very high (I² 84%), suggesting the effect depends heavily on unmeasured factors. Glucose and insulin resistance showed improvements (glucose −0.29 mmol/L, insulin resistance −0.99 on HOMA scale), but with very high heterogeneity (I² 76% and 66% respectively), limiting confidence. When comparing one type of physical activity to another (e.g., high-intensity interval training versus moderate-intensity continuous training), all evidence was very low-certainty, meaning it is unclear which type works best. Notably, none of the 30 studies enrolled adolescents with disabilities, provided minimal data on contextual factors (family support, socioeconomic barriers, school environment), or tracked outcomes into adulthood—critical gaps since short-term weight loss in adolescence may not persist or translate to adult health gains.